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The Apollo Experience Report: Thermal Protection Subsystem explains that there are three sections to the Apollo heat shield:

  • The aft heat shield, at the "base" of the cone and adjacent to the SM. This is probably what you think of when you hear "heat shield".

  • The crew compartment heat shield, on the "sides" of the cone. It covered the main hatch and has many openings for windows, RCS engines, antennas, and vents.

  • The forward heat shield, at the "tip" of the cone. It covered the docking tunnel.

Apollo heat shields

All three heat shields were made of a fiberglass honeycomb filled with epoxy.

The forward heat shield was automatically ejected at 24,000 feet by a baroswitch (with manual backup switches). It had its own parachute, landed separately from the CM, and had its own recovery helicopter. The other two heat shields remained attached to the CM. The drogue, pilot, and main parachutes were completely separate from the heat shield chute, and began their deployment sequence two seconds after 24,000 feet.

Where are the forward heat shields today? Are they with their respective command modules? Were some lost to the ocean? In some government warehouse next to the Ark of the Covenant? I can only account for Apollo 15's, which was extensively examined as a possible cause of the failure of one main parachute on that flight.

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  • $\begingroup$ The heat shield is made from stainless steel panels and a fiber-glas honeycomb bonded with adhesive tape. The ablative material selected for the TPS is designated Avco 5026-39G and consists of an epoxy-novalac resin reinforced with quartz fibers and phenolic microballoons. $\endgroup$
    – Uwe
    Commented Jun 18, 2019 at 13:55
  • $\begingroup$ @Uwe: Very good, but how does that answer the question? $\endgroup$
    – DrSheldon
    Commented Jun 18, 2019 at 14:11
  • $\begingroup$ It does not answer the question, but the honeycomb was not made from stainless steel. Using a thermal isolator like fiber-glas was a better choice for the heat shield. $\endgroup$
    – Uwe
    Commented Jun 18, 2019 at 14:20
  • $\begingroup$ @Uwe: Thanks. Confirmed by tech note D-7564, and the question corrected. $\endgroup$
    – DrSheldon
    Commented Jun 18, 2019 at 14:28
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    $\begingroup$ This PDF suggests to me that the forward heat shield’s chute may have just been a small drag chute to pull it quickly away from the CM rather than intended for particularly gentle splashdown: ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20090016307.pdf — since the forward heat shield was an important component of the TPS, they certainly would have wanted to recover it for analysis during the early missions, and even for later ones in case of some anomaly. $\endgroup$
    – Russell Borogove
    Commented Nov 12, 2019 at 23:40

2 Answers 2

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Here is what I have found:

Apollo 4- Managed by the Smithsonian, is not on display there. May be on loan, can't figure out where.

Apollo 17- On display at the Kansas Cosmosphere

Apollo 15- Was recovered for sure, as y you mentioned.

It seems like not as much effort was put forward to recovering these. Apollo 4 was probably recovered because it was the first mission flown. The others seem to have been missions of opportunity.

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Except for the Apollo 15 and 17 articles, it appears the Forward Heat Shields are resting at the bottom of the ocean. Somewhere.

From Wikipedia:

At 24,000 feet (7.3 km) the forward heat shield was jettisoned using four pressurized-gas compression springs. The drogue parachutes were then deployed, slowing the spacecraft to 125 miles per hour (201 kilometres per hour).

The Forward Heat Shields were the first thing ejected, before any parachutes. It's safe to say they weren't recovered unless there is specific information otherwise. A brief discussion post indicates that the 15 and 17 articles were recovered, but I've not seen anything discussing such for the other vehicles.

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